Advice on 1st sub

Discussion in 'Home Theater Projects' started by GaryLB, Oct 21, 2003.

  1. GaryLB

    GaryLB Auditioning

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    I want to build my first sub for 75% HT/25% music in an 11 X 14 room with an 8'9" ceiling. I was going to use a Tempest with an Adire 250W amp, but after reading through some threads here, it seems the Rythmik A350-Basic is considered a better way to go.

    I was planning on making a vented box using the Adire Alignment. The building instructions say that a void free plywood like baltic birch is the first choice for material, so I was going to construct the sub from baltic birch and use some basic joinery to hold it all together, as I have a small wood shop in my basement.

    I was hoping to get some input on the amp/driver selection, whether the vented adire alignment of the dimensions given on the adire website (214L 37.5"hX22"wX22"d) would be good for my uses/room, and if there are any special considerations to using ply vs. MDF. Any other advice/suggestions would be appreciated.

    Thanks,
    Gary
     
  2. Darren_T

    Darren_T Second Unit

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    I built this very sub with the 250 watt plate amp. I'd skip the baltic birch, too expensive and in my opinion not as fit for the job as MDF. MDF is easy to work, cheap, and machines beautifully. The 214L Adire alignment sub is an excellent choice and the Rythmik amp is also an excellent choice. I built another Tempest with that amp and it worked great.

    Tips:
    1. Use MDF. It's cheap, easy to work, and heavy/dense
    2. no screws! use clamps and brads with a good yellow glue
    3. Make accurate cuts with 90 degree angles for a tight and solid joint
    4. no need for fancy joints. Simple butt joints are strong enough
    5. Don't compensate for bad cuts/joints with extra clamping pressure. You'll starve the joint of glue and it WILL fail with time

    See my sub at: www.thomaswoodcraft.com

    Don't forget this alignment is meant to be down-firing. It won't sound right front firing, it needs the load from the floor.

    Oh, I'm also 75% HT and 25% music on average. It hits nice and looooow [​IMG]

    I think you are set. Go for it.
     
  3. MarcQuin

    MarcQuin Auditioning

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    I also just finished this exact sub & alignment except using the PE 250W amp. I was a little worried it would not be enough considering my living room and kitchen are fully open to each other so I was looking at a space of about 30' x 22'6 with a 12' vaulted ceiling. There was no need to worry though. The thing is a beast. Sounds and feels like the house is coming down.[​IMG]

    I had to build mine length wise instead of tall so it was a bit different but the internal dimensions were the same. I have to agree that 3/4" MDF is the way to go though. Once you get it built you will understand. With the internal bracing it is very solid. I also used the brad nailer with yellow wood glue and that is definitely how I would do it if I were to build another.

    Right now I'm almost 100% HT because I do not enjoy listing to music through my current speakers so I can't really comment on it musically. That will change soon though.

    It's a sweet sub. I don't think you will be dissapointed.

    Cheers,
    Marc
     
  4. ThomasW

    ThomasW Cinematographer

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  5. Darren_T

    Darren_T Second Unit

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  6. ThomasW

    ThomasW Cinematographer

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  7. Darren_T

    Darren_T Second Unit

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  8. Darren_T

    Darren_T Second Unit

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    Hey Gary,

    Sorry this turned into some pissing match. No reason for that. Not sure why ThomasW felt the need to put me on the defensive. It really helps nobody.

    Anyway, my advice is sound. Especially the woodworking advice. By all means, try the subwoofer as a front firing with this alignment and see how it works for you if you decide you'd like to try that. It may work with your room acoustics but I think you'll probably experience the same thing I did. I think you'll be very happy with your choice. I'm really happy with my Tempest although I'm building a new AV15 enclosure now. [​IMG] I just had the upgrade urge, happens to the best of us.

    Darren
     
  9. Dean-P

    Dean-P Stunt Coordinator

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  10. ThomasW

    ThomasW Cinematographer

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    Darren

    My intent was not to put anyone on the defensive. The statement regarding the superiority of one driver orientation vs another, runs a bit counter to my experiences in sub building. So I was just curious as to the genesis of the statement.

    I emailed Adire for comment on a down firing vs front firing versions of their alignments.

    FWIW, SVS does use down firing to augment the output of the their subs. One can see the very short distance between the driver and the bottom plate. This short distance creates a resistive load on the driver, which in turn boosts output at certain frequencies. With the Adire designs and their 4" leg height this doesn't appear to be the case. The 4" leg height is probably too tall for any significant loading to occur.

    Generally speaking use of a bottom plate will of course be beneficial if a downward firing sub is on a soft surface like carpet. And it will prevent 'walking' on any surface if extremely high output levels are being used.

    I'll post Adire's reply when it arrives.

    Regard
    Thomas
     
  11. Darren_T

    Darren_T Second Unit

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    That's fine. If you are questioning me then do it. Don't post some pompus statement making a demand for me to supply proof and a credible source. Instead use communication skills to say something like the following:

    "My experience has been different than Darren's. I find there is no difference myself."

    It's called being polite. Your statements were terse and in any social situation would most likely promote a defensive stance which I took. I don't take BS from anyone.

    Like I said. If you disagree buck up and say it. Don't play games.

    Darren
     
  12. Darren_T

    Darren_T Second Unit

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  13. Neil Joseph

    Neil Joseph Lead Actor

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    Real Name:
    Neil Joseph
    ThomasW
     
  14. Craig_B

    Craig_B Agent

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    Boy, a simple "what do you guys think of this sub?" thread turned ugly fast. The funny part is that GaryLB did not even asked about down firing vs front firing. Darren_T gave some excellent suggestions that pertained exactly to the questions asked and just because of one comment he made about down firing vs front firing, the thread has been hijacked and is on the verge of being shut down. How does that help anyone?

    Back on topic, my question is why would Adire reccomend Baltich Birch as their top choice for building this sub if it was inferior to MDF? I understand that it is more expensive, but assuming that money was not an issue and since the birch has the advantage of staining directly rather than messing with veneering, what is the downside to using this material and why is MDF better?
     
  15. GaryLB

    GaryLB Auditioning

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    Thanks for the replies to my question. While I have a table saw, router table, lots of clamps, etc. in my shop, I don't have a compressor/nail gun. Would you guys still recommend using brads on the MDF but with a hammer and nail set?

    As for Craig's question, I know the MDF is considerably less expensive than the void-free plywoods, but believe it is also harder on carbide tipped blades and bits, will likely make a bigger mess than the plywoods when worked (I don't have a dust collection system other than a vacuum and broom [​IMG] ), and requires veneering. So are there advantages to using MDF over ply other than cost?
     
  16. ThomasW

    ThomasW Cinematographer

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  17. Jack Gilvey

    Jack Gilvey Producer

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    Thomas right again? Surprize! [​IMG]
     
  18. Arthur_King

    Arthur_King Stunt Coordinator

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    Gentlemen, Gentlemen,

    It may very well be that in Darren's situation, with Darren's room, in Darren's configuration, it sounds better bottomfiring. Maybe its getting a big of loading from the floor. Maybe the 2ft difference in position moved the sub a bit away from a null and that helped make it sound better. No matter, I think Thomas was simply asking because of the CERTAINTY of the statement. Like "everything I know and everything I've read says this is true" and Thomas said, "Oh, what did you read and what do you know?"

    No need to lay our weiners on the table and whip out the measuring tape... Its all in HOW you use it.

    Daffy Arthur King
     
  19. ThomasW

    ThomasW Cinematographer

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    Gary/Craig,

    There are basically 2 ways to construct a box.

    1)low mass, low density, high Fs, = baltic ply. This design has the Fs (resonant frequency) of the box itself operating at frequencies higher than those where the driver is working.

    2)high mass, high density, low Fs = MDF. This has the Fs of the box lower than the frequencies where the driver is operating.

    The goal is to build a box where there is no wall vibration/flex. Since MDF is inherently less rigid than Baltic ply it (the MDF box), requires more bracing to control vibrations.
     
  20. ThomasW

    ThomasW Cinematographer

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